Copolymer useful as a pour point depressant for a lubricating oil

ABSTRACT

A copolymer useful as a pour point depressant for hydrocarbon lubricating oils includes from about 15 mole percent to about 67 mole percent comonomeric units derived from a (C 8  -C 15 ) alkyl (meth)acrylate monomer, from about 3 mole percent to about 40 mole percent comonomeric units derived from a (C 16  -C 24 ) alkyl (meth)acrylate monomers and from greater than 30 mole percent to about 65 mole percent comonomeric units derived from a (C 1  -C 4 )alkyl (meth)acrylate monomer.

The present application is a divisional application of U.S. patentapplication Ser. No. 08/055,131 for a "COPOLYMER USEFUL AS A POUR POINTDEPRESSANT FOR A LUBRICATING OIL", filed Apr. 30, 1993, now U.S. Pat.No. 5,312,884 by R. H. Gore and J. H. O'Mara.

TECHNICAL FIELD

The present invention relates to certain alkyl (meth)acrylate copolymersand their use as additives for lowering the pour point of hydrocarbonlubricating oils.

BACKGROUND

Lubricating base oils, e.g., commercial petroleum distillate oils,commonly contain paraffinic hydrocarbons that crystallize upon coolingthereby significantly increasing the viscosity of the oil. At asufficiently low temperature, the crystalline wax structure ultimatelycauses gelation of the base oil. The low temperature fluidity ofpetroleum distillate oils can be improved by dewaxing and such oils aretypically, dewaxed to a pour point, i.e., the lowest temperature atwhich the oil remains fluid, of about -15° C. Further lowering of thepour point is typically achieved by the use of a pour point loweringadditive, i.e., a "pour point depressant", that further lowers the pourpoint of the dewaxed oil, typically down to about -30° C.

The composition of petroleum distillate oils is variable and therelationship between base oil composition and the composition of thoseadditives effective in lowering the pour point of any particular baseoil is often poorly characterized. It is, therefore, not always possibleto reliably prescribe a particular pour point depressant composition foreffectively treating a particular base oil, i.e., treatment of anyparticular oil with pour point depressant remains, to a large extent, anempirical undertaking.

Poly(alkyl methacrylate) pour point depressants comprising higher alkylesters, e.g., those including 12 or more carbon atoms per alkyl group,are known. It is believed that the elongated paraffin-like alkylportions of such pour point depressants are incorporated into thegrowing paraffin crystals, thereby inhibiting further crystal growth andpreventing formation of an extensive interlocking paraffin crystalstructure. In U.S. Pat. No. 4,867,894, Pennewiss et al disclose apoly(alkyl methacrylate) pour point depressant whereto from 10 to 30,preferably 10 to 20, mote percent methylmethacrylate is copolymerizedwith alkylmethacrylate monomers having relatively long i.e., C₁₆ andhigher, alkyl groups to form a pour point depressant additive. Pennewisset al teach that such an additive has a lower cost due to substitutionof relatively low cost methyl methacrylate for a portion of relativelyhigh cost higher alkyl esters and that, within the disclosed ranges ofmethyl methacrylate mole percent, such a substitution does not diminishthe effectiveness of the additive as a pour point depressant.

There is a constant effort in the art to provide pour point depressantsthat provide cost effective performance in a wide range of lubricatingoil base stocks.

SUMMARY OF THE INVENTION

A random copolymer is disclosed. The copolymer includes front about 15mole percent to about 67 mole percent first repeating units wherein eachof the first repeating units has the structural formula: ##STR1##wherein each occurrence of R₁ is independently H or methyl and eachoccurrence of R₂ is independently selected from the group consisting of(C₈ -C₁₅)alkyl.

The copolymer includes from about 3 mole percent to about 40 molepercent second repeating units, wherein each of the second repeatingunits have the structural formula: ##STR2## wherein each occurrence ofR₃ is independently H or methyl and each occurrence of R₄ isindependently selected from the group consisting of (C₁₆ -C₂₄) alkyl.

The copolymer includes from greater than 30 percent to about 65 molepercent third repeating units, wherein each of the third repeating unitshave the structural formula: ##STR3## wherein each occurrence of R₅ isindependently H or methyl and each occurrence R₆ is independentlyselected from the group consisting of (C₁ -C₄)alkyl.

The copolymer of the present invention provides high performance as apour point lowering additive in a wide range of lubricating oil basestocks at a reduced cost.

A method for making a copolymer for use in lowering the pour point of alubricating oil is disclosed. The method includes copolymerizing amixture of monomers in a hydrocarbon diluent, wherein the monomermixture includes from about 15 mole percent to about 67 mole percent ofa (C₈ -C₁₅)alkyl (methacrylate, monomer, from about 3 mole percent toabout 40 mole percent of a (C₁₆ -C₂₄)alkyl (meth)acrylate monomer, andfrom greater than 30 mole percent to about 65 mole percent of a (C₁-C₄)alkyl (meth)acrylate monomer.

A pour point depressant composition is disclosed. The compositionincludes about 100 parts by weight of the copolymer of the presentinvention and from about 15 to about 600 parts by weight of ahydrocarbon diluent.

A method for lowering the pour point of a lubricating oil base stock isdisclosed. The method includes adding to the base stock from about 0.02weight percent to about 0.5 weight percent of the copolymer of thepresent invention.

A lubricating oil composition is disclosed. The composition includes alubricating oil base stock and from about 0.02 weight percent to about0.5 weight percent of the copolymer of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The random copolymer of the present invention includes from about 15mole percent to about 67 mole percent first repeating units, each havingthe structural formula (1): ##STR4## wherein each occurrence of R₁ isindependently H or methyl and each occurrence of R₂ is independentlyselected from the group consisting of (C₈ -C₁₅)alkyl

Preferably, R₁ is methyl.

As used herein, (C₈ -C₁₅)alkyl means any straight or branched alkylgroup having 8 to 15 carbon atoms per group, e.g., octyl, nonyl, decyl,isodecyl, undecyl, lauryl, tridecyl, myristyl, pentadecyl. Preferably,R₂ is (C₁₀ -C₁₅)alkyl. More preferably, R₂ is selected from the groupconsisting of isodecyl, lauryl, tridecyl, myristyl, pentadecyl andmixtures thereof.

Preferably, the copolymer includes front about 25 mole percent to about60 mole percent first repeating units. More preferably, the copolymerincludes from about 25 mole percent to about 40 mole percent firstrepeating units.

The copolymer includes from about 3 mole percent to about 40 molepercent second repeating units, each having the structural formula (2):##STR5## wherein each occurrence of R₃ is independently H or methyl andeach occurrence of R₄ is independently selected from the groupconsisting of (C₁₆ -C₂₄) alkyl.

Preferably, R₃ is methyl.

As used herein, (C₁₆ -C₂₄) alkyl means any straight or branched alkylgroup having 16 to 24 carbon atoms per group, e.g., stearyl, cetyl,heptadecyl, nonadecyl, eicosyl. Preferably, and R₄ is (C₁₆ -C₂₄)alkyl.More preferably, R₄ is selected from the group consisting of stearyl,cetyl, eicosyl and mixtures thereof.

Preferably, the copolymer includes from about 10 mole percent to about35 mole percent second repeating units. More preferably, the copolymerincludes from about 15 mole percent to about 30 mole percent secondrepeating units.

The copolymer includes from greater than 30 mole percent to about 67mole percent third repeating units, each having the structural formula(3): ##STR6## wherein each occurrence of R₅ is independently H or methyland each occurrence of R₆ is independently selected from the groupconsisting of (C₁ -C₄)alkyl.

Preferably, R₅ is methyl.

As used herein, (C₁ -C₄)alkyl means any straight or branched alkyl grouphaving 1 to 4 carbon atoms per group, e.g., methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, t-butyl. Preferably, R₆ is selected fromthe group consisting of methyl, n-butyl, isobutyl and mixtures thereof.Most preferably, R₆ is methyl.

Preferably, the copolymer includes from about 32 mole percent to about50 mole percent third repeating units. More preferably, the copolymerincludes from about 35 mole percent to about 45 mole percent thirdrepeating units.

The copolymer of the present invention has a number average molecularweight, determined, e.g., by gel permeation chromatography, from about20,000 to about 80,000 preferably from about 25,000 to about 70,000, andmost preferably from about 28,000 to about 60,000.

The copolymer of the present invention has a weight average molecularweight, determined, e.g., by gel permeation chromatography, from about50,000 to about 200,000, preferably from about 50,000 to about 175,000,and most preferably from about 50,000 to about 100,000.

The copolymer of the present invention can be made by free radicalinitiated polymerization of alkyl (meth)acrylate monomers. Theterminology "(meth)acrylate" is used herein to generally refer toacrylate esters, methacrylate esters and mixtures thereof. Commerciallyavailable alkyl (meth)acrylate monomers may be, and typically are,mixtures of esters. Such mixtures are typically referred to, and arereferred to herein, using a contracted version of the names of the esterspecies predominating in the mixture, e.g., "lauryl-myristylmethacrylate", "cetyl-eicosyl methacrylate", "cetyl-stearylmethacrylate", "dodecyl-pentadecyl methacrylate".

In a preferred embodiment, each of the first repeating units of thecopolymer of the present invention is derived from a (C₈ -C₁₅)alkylmethacrylate monomer, preferably a (C₁₀ -C₁₅)alkyl methacrylate monomer.

As used herein, "(C₈ -C₁₅)alkyl methacrylate monomer" means an alkylester of methacrylic acid having a straight or branched alkyl group of 8to 15 carbon atoms per group, including, e.g., octyl methacrylate, nonylmethacrylate, decyl methacrylate, isodecyl methacrylate, undecyimethacrylate, lauryl methacrylate, tridecyl methacrylate, myristylmethacrylate, pentadecyl methacrylate and mixtures thereof.

In a particularly preferred embodiment, each of the first repeatingunits of the copolymer of the present invention is derived from amonomer selected from the group consisting of isodecyl methacrylate,lauryl methacrylate, myristyl methacrylate, tridecyl methacrylate,pentadecyl methacrylate and mixtures thereof, e.g., lauryl-myristylmethacrylate, dodecyl-pentadecyl methacrylate.

In a preferred embodiment, each of the second repeating units of thecopolymer of the present invention is derived from a (C₁₆ -C₂₄)alkylmethacrylate monomer, preferably a (C₁₆ -C₂₄)alkyl methacrylate monomer.

As used herein, "(C₁₆ -C₂₄)alkyl methacrylate monomer" means an alkylester of methacrylic acid having a straight or branched alkyl group of16 to 24 carbon atoms per group, including, e.g., stearyl methacrylate,cetyl methacrylate, heptadecyl methacrylate, nonadecyl methacrylate,eicosyl methacrylate and mixtures thereof.

In a particularly preferred embodiment, each of the second repeatingunits or copolymer of the present invention is derived from a monomerselected from the group consisting of stearyl methacrylate, cetylmethacrylate, eicosyl methacrylate and mixtures thereof, e.g.,cetyl-stearyl methacrylate, cetyl-eicosyl methacrylate.

In a preferred embodiment, each of the third repeating units of thecopolymer of the present invention is derived from a (C₁ -C₄)alkylmethacrylate monomer.

As used hereto, "(C₁ -C₄)alkyl methacrylate monomer" means a alkyl esterof methacrylic acid having a straight or branched alkyl group of 1 to 4carbon atoms per group, including, e.g., methyl methacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate.

In a particularly preferred embodiment, the third repeating units of thecopolymer of the present invention are derived from a monomer selectedfrom the group consisting of methyl methacrylate, n-butyl methacrylate,isobutyl methacrylate and mixtures thereof.

Most preferably, each of the third repeating units is derived frommethyl methacrylate. Use of methyl methacrylate as the (C₁ -C₄)alkylmonomer of the present invention provides the greatest cost advantagedue to the relatively low cost of that monomer relative to higher alkyl(meth)acrylate monomers.

In a particularly preferred embodiment, the copolymer of the presentinvention includes about 43.9 mote percent first repeating units, eachderived from lauryl methacrylate, about 14.7 mole percent secondrepeating units, each derived from cetyleicosyl methacrylate, and about41.4 mole percent third repeating, each derived from methylmethacrylate.

In an alternative particularly preferred embodiment, the copolymer ofthe present invention includes about 35.2 mole percent first repeatingunits, each derived from lauryl methacrylate, about 22.5 mole percentsecond repeating units, each derived from cetyl-eicosyl methacrylate,and about 42.3 mole percent third repeating units, each derived frommethyl methacrylate.

A reaction mixture including a diluent, selected relative amounts ofrespective selected alkyl (meth)acrylate monomers, a polymerizationinitiator and a chain transfer agent is prepared.

The diluent may be any inert hydrocarbon and is preferably a hydrocarbonlubricating oil which is compatible with or identical to the lubricatingoil in which the copolymer is to be subsequently used. The mixtureincludes, e.g., from about 15 to about 400 parts by weight (pbw) diluentper 100 pbw total monomers and, more preferably, from about 50 to about200 pbw diluent per 100 pbw total monomers. As used herein, "totalmonomer charge" means the combined amount of all monomers in theinitial, i.e., unreacted, reaction mixture.

In a preferred embodiment of the process of the present invention, thetotal monomer charge includes from about 15 mole percent to about 65mole percent, more preferably from about 25 mole percent to about 60mole percent, and most preferably from about 25 mole percent to about 40mole percent, (C₈ -C₁₅)alkyl methacrylate monomer. In the preferredembodiment of the process, the monomer portion of the reaction mixtureincludes from about 3 mole percent to about 40 mole percent, morepreferably from about 10 mole percent to about 35 mole percent, and mostpreferably from about 15 mole percent to about 30 mole percent, (C₁₆-C₂₄)alkyl methacrylate monomer. In the preferred embodiment, themonomer portion of the reaction mixture includes from greater than 30mole percent to about 65 mole percent, preferably from about 32 percentto about 50 percent, and most preferably from about 35 mole percent toabout 45 mole percent, (C₁ -C₄)alkyl methacrylate monomer.

Suitable polymerization initiators include initiators which disassociateupon heating to yield a free radical, e.g., peroxide compounds such asbenzoic peroxide, t-butyl peroctoate, cumene hydroperoxide, and azocompounds such as azoisobutylnitrile, 2,2'-azobis(2-methylbutanenitrile). T-butyl peroctoate is preferred as thepolymerization initiator. The mixture includes, e.g., from about 0.25pbw to about 1.0 pbw initiator per 100 pbw total monomer charge and,more preferably, from about 1.0 pbw to about 0.8 pbw initiator per 100pbw total monomer charge.

Suitable chain transfer agents include those conventional in the art,e.g., dodecyl mercaptan, ethyl mercaptan. Dodecyl mercaptan is preferredas the chain transfer agent. The selection of the amount of chaintransfer agent to be used is based on the desired molecular weight ofthe polymer being synthesized. The reaction mixture typically includes,e.g., from about 0.5 pbw to about 1.0 pbw chain transfer agent per 100pbw total monomer charge and more preferably includes from about 0.6 pbwto about 0.8 pbw chain transfer agent per 100 pbw total monomer charge.

The reaction mixture is charged to a reaction vessel that is equippedwith a stirrer, a thermometer and a reflux condenser and heated withstirring under a nitrogen blanket to a temperature from about 90° C. toabout 125° C. The batch is then maintained at a temperature from about90° C. to about 125° C. for a period of about 0.5 hours to about 6 hoursto carry out the copolymerization reaction.

In a preferred embodiment, a portion, e.g., about 25 to 60%, of thereaction mixture is initially charged to the reaction vessel and heated.The remaining portion of the reaction mixture is then metered into thereaction vessel, with stirring and while maintaining the temperature ofthe batch within the above described range, over a period of about 0.5hours to about 3 hours.

In the preferred embodiment of the process, an additional amount ofinitiator, e.g., from about 0.1 pbw to about 0.5 pbw initiator per 100pbw total monomer charge, is then charged to the reaction vessel and thebatch is then maintained at a temperature within the above-specifiedrange with stirring for an additional period of about 0.5 hours to about6 hours.

A viscous solution of the copolymer of the present invention in thediluent is obtained as the product of the above described process.

A base oil is treated with the copolymer of the present invention in aconventional manner, i.e., by adding the copolymer to the base oil toprovide a lubricating oil composition having a desired pour point. Apreferred embodiment of a lubricating oil includes from about 0.05 pbwto about 1.0 pbw copolymer per 100 pbw base oil. In a particularlypreferred embodiment, the copolymer is added to the base oil in the formof a relatively concentrated solution of the copolymer in a diluent,e.g., a solution about 100 pbw of the copolymer dissolved in from about15 pbw to about 600 pbw of the hydrocarbon diluent used in the abovedescribed polymerization process.

A copolymer of the present invention may advantageously be used incombination with another pour point lowering copolymer, e.g., with adifferent embodiment of the copolymer of the present invention or with acopolymer selected from known poly(alkyl (meth)acrylate) copolymers, toprovide pour point lowering copolymer blends, e.g., blends includingfrom about 50 pbw to about 100 pbw of a first embodiment of thecopolymer of the present invention per 100 pbw of a second pour pointlowering copolymer. Such blends may be custom formulated for optimalperformance in a particular base oil.

A lubricating oil composition may include other additives in addition tothe copolymer of the present invention, e.g., oxidation inhibitors suchas dithiophosphate, detergent/corrosion inhibitors such as overbasedmetal sulfonates, antifoamants such as silicone polymers and viscosityindex improvers such as poly(alkyl (meth)acrylate) copolymers, olefincopolymers, hydrogenated styrene-butadiene copolymers.

EXAMPLE 1

A monomer mix was prepared from 120 grams cetyl-eicosyl methacrylate(100% basis. 95.5% purity), 200 grams lauryl-myristyl methacrylate (100%basis, 97.5% purity), 80 grams methyl methacrylate (100% basis, 99.5%purity), 2.32 grams of a 50% solution of t-butyl peroctoate in mineralspirits, 2.80 grams dodecyl mercaptan, and 0.68 grams paraffinic baseoil (100N oil). Part of the above monomer mix (30%) and 3.05 parts 100Noil were charged to a nitrogen flushed kettle fitted with a thermometerand a Thermowatch™ temperature controller, a water-cooled refluxcondenser with nitrogen outlet, a stirrer, a nitrogen inlet, and anaddition funnel to control the addition of the monomer mix. The contentsof the kettle were heated to 105° C. with provisions for cooling tomaintain the batch temperature below 120° C., thereby controlling anyexotherm. The batch was maintained at 105° C. for about 5 minutes andthen heated slowly to 115°-120° C. The remainder of the monomer mix wasadded uniformly over a 60 minute period after the batch temperaturereached 115° C. The temperature was maintained at 115°-120° C. for 30minutes following completion of the monomer feed. At this point aninitiator feed of 1.6 grams of a 50% solution of t-butyl peroctoate inmineral spirits and 33.6 grams 100N oil was added to the flask over 60minutes at 115°-120° C., after which the batch was held at the sametemperature for an additional 30 minutes.

The process yielded a viscous solution of a copolymer in the base oil.Monomer conversion to polymer was approximately 97%. The polymer soformed exhibited a number average molecular weight of 31,200 and aweight average molecular weight of 81,300, each measured by gelpermeation chromatography.

Approximately 39.92 parts 100N oil were then added to bring the batch toa final polymer solids content of 64%.

EXAMPLES 2 to 19 and C1 to C4

The copolymers of Examples 2 to 19 and C1 to C4 were each made accordingto the process described above in Example 1, except that differentamounts of the respective comonomers were used. Table 1 below sets forththe relative amounts (mole %) of the respective comonomers, i.e.,cetyl-eicosyl methacrylate (CEMA), laurylmyristyl methacrylate (LMA),methyl methacrylate (MMA), isodecyl methacrylate (IDMA), for each ofthose Examples.

                  TABLE 1                                                         ______________________________________                                                       CEMA/LMA/MMA/BMA/IDMA                                          EXAMPLE NUMBER (mole %)                                                       ______________________________________                                         2             19.8/56.6/33.6/0/0                                              3             18/36.4/45.6/0/0                                                4             17.4/33.5/49.1/0/0                                              5             16.4/28.0/55.6/0/0                                              6             11.3/33.9/54.8/0/0                                              7             16.7/50/33.3/0/0                                                8             14.7/43.9/41.4/0/0                                              9             19.8/46.6/33.6/0/0                                             10             18.6/39.6/41.8/0/0                                             11             25.7/40.2/34.1/0/0                                             12             22.5/35.2/42.5/0/0                                             13             30.6/34.9/34.5/0/0                                             14             28.6/28.4/43/0/0                                               15             7.2/52.2/40.6/0/0                                              16             21.3/0/39.9/0/38.8                                             17             12.2/46.7/41.1/0/0                                             18             14.1/42.2/0/43.6/0                                             19             15.4/46.0/0/38.6/0                                             C1             25.1/74.9/0/0/0                                                C2             39/61/0/0/0                                                    C3             23/67/13/0/0                                                   C4             21.3/54.6/24.1/0/0                                             ______________________________________                                    

EXAMPLES 20A to 20GG

Each of Examples 20A to 20T and 20Z to 20 BB were made by preparing asolution of 0.15 wt % (polymer solids) of a respective one of thecopolymers of Examples 1-6 and C1, C3, C4 in a base oil. Each ofExamples 20U to 20TY and 20CC to 20 GG were made by preparing a solutionof 0.19 wt% (polymer solids) of a respective one of the copolymers ofExamples 15-19 in a base oil. The pour point of each of Example soformed was measured by both ASTM D-97-87 and "Cycle C" test methods. Thesonic shear index of each of the Examples was measured by the method ofASTM D 26303-91 following 12.5 minutes sonic shearing.

The copolymer (Example No.), the lubricating oil base stock (A=Exxon100N (ASTM pour point=-21° C.), B=Exxon 600N, C=Quaker State Congo 125N,D=Sentry 70 (ASTM pour point =-15° C.)), the ASTM pour point (°C.) andthe Cycle C pour point (°C.) are each given below in Table 2 for each ofExamples 20A to 20GG. Sonic Shear Index (SSI) values are also given forExamples 20A-20I, 20O-20T and 20Z-20BB.

                  TABLE 2                                                         ______________________________________                                                 ADDI-             ASTM   CYCLE C                                              TIVE              POUR   POUR                                        EXAMPLE  (EX.     BASE     POINT  POINT                                       NO.      NO.)     STOCK    (°C.)                                                                         (°C.)                                                                          SSI                                 ______________________________________                                        20A      C1       A        -39    -33     16.1                                20B      C3       A        -45    F-39    19.2                                20C      C4       A        -39    F-39    22.9                                20D       2       A        -39    F-39    24.9                                20E       1       A        -39    F-39    15.3                                20F       3       A        -39    F-39    17.6                                20G       4       A        -39    -39     16                                  20H       5       A        -36    F-39    14.2                                20I       6       A        -39    -39     16.0                                20J      15       A        -27    -33     --                                  20K      16       A        -27    -27     --                                  20L      17       A        -33    -36     --                                  20M      18       A        -33    F-39    --                                  20N      19       A        -36    F-39    --                                  20O      C1       B        -20    -24     16.1                                20P       2       B        -21    -24     24.9                                20Q       1       B        -24    -24     15.3                                20R      C1       C        -33    -33     16.1                                20S       2       C        -30    -33     24.9                                20T       1       C        -36    -33     15.3                                20U      15       C        -33    -33     --                                  20V      16       C        -21    -24     --                                  20W      17       C        -36    -30     --                                  20X      18       C        -36    -33     --                                  20Y      19       C        -36    -33     --                                  20Z      C1       D        -27    -30     16.1                                20AA      2       D        -24    -30     24.9                                20BB      1       D        -24    -30     19.2                                20CC     15       D        -12    -12     --                                  20DD     16       D        -13    -12     --                                  20EE     17       D        -15    -12     --                                  20FF     18       D        -15    -12     --                                  20GG     19       D        -12    -12     --                                  ______________________________________                                    

The viscosity of each of Examples 20A, 20E, 200 20Q, 20R, 20T, 20Z and20BB was measured at -15, -20, -25, -30, and -35° C. using a mini rotaryviscometer (MRV) according to the method of ASTM D 4684-89.

Results are set forth below in Table 3 as apparent viscosity (Poise) ateach temperature for each of those Examples. A Borderline PumpingTemperature (BPT) is also set forth for each Example. The notation"TFTM" (too fluid to measure) is used in Table 3 to indicate that theviscosity of a particular sample was too low to measure in using the MRVat the indicated temperature

                  TABLE 3                                                         ______________________________________                                        EX.   -15°                                                                           -20°    -30°                                      NO.   C.      C.      -25° C.                                                                       C.    -35° C.                                                                       BPT                                 ______________________________________                                        20A   --      --      TFTM   28.3    92.3 >-35                                20E   --      --      TFTM   27.6    82.8 >-35                                20O   119     280     1168   --    --     -19.8                               20Q   125     269     1057   --    --     -19.9                               20R   --      --         29.0                                                                              69.7  182    -36.9                               20T   --      --         17.7                                                                              63.1  200    -35.8                               20Z   136     276      963   --    --     -19.8                               20BB  112     235      778   --    --     -20.8                               ______________________________________                                    

EXAMPLES 21 AND C22

Two series of samples, 21A to 21H and C22A to C22G, were made bydissolving the respective copolymers of Examples 1 and C1 in a base oil(Quaker State 125N) to provide formulations having the compositionsgiven in Table 4.

The ASTM D 97-87 pour point (°C.) and Cycle C pour point (°C.) were eachmeasured for each sample and are given in Table 4.

                  TABLE 4                                                         ______________________________________                                                 WT %        ASTM        CYCLE                                        EXAMPLE  POLYMER     POUR        C POUR                                       NO.      SOLIDS      POINT (° C.)                                                                       POINT (° C.)                          ______________________________________                                        Base Stock                                                                             0.00        -12         -12                                          21A      0.16        -36         -33                                          21B      0.12        -36         -33                                          21C      0.11        -36         -33                                          21D      0.08        -36         -30                                          21E       0.053      -30         -30                                          21F      0.04        -27         -30                                          21G      0.32        -30         -30                                          21H       0.026      -27         -33                                          C22A     0.15        -36         -33                                          C22B      0.112      -36         -30                                          C22C     0.10        -36         -30                                          C22D      0.075      -33         -30                                          C22E     0.05        -33         -30                                          C22F      0.038      -33         -33                                          C22G      0.025      -33         -27                                          ______________________________________                                    

EXAMPLES 23A TO 23J

The copolymers of Examples C1, C2 and 9 to 16 were added to an SAE15W-40 lubricating oil (0.15 wt % copolymer solids in Imperial PL23720-1oil). The shear stability of each of the Examples was measured by ASTM D2603-1 oil). The viscosity of each of the samples was measured by ASTM D468449 at -20° C. and -25° C. using a mini rotary viscometer. The pourpoint of each of the samples was measured according to the Cycle C testmethod.

The shear stability following 12.5 minute sonic shear (% SLDTP), thepercent bulk (weight %), the Cycle C pour point (°C.) and the D 4684-89apparent viscosity (Poise) at -20° C. and -25° C. is forth below inTable 4 for each of the Examples.

                  TABLE 5                                                         ______________________________________                                             ADDI-                  CYCLE                                                  TIVE                   C      Viscosity                                  EX.  EX.     %        %     POUR   (Poise)                                    NO.  NO.     SLDTP    BULK  POINT  -20° C.                                                                       -25° C.                      ______________________________________                                        23A  C1      16.1     0.260 -18     9036* Solid                               23B   9      16.6     0.258 -30     3133* Solid                               23C  10      12.3     0.260 -30    154    427                                 23D  11      13.9     0.258 -36    162    458                                 23E  12      17.2     0.258 -36    142    411                                 23F  C2      15.3     0.254 -36    156    430*                                23G  13      13.3     0.179 -36    161    432*                                23H  14      16.0     0.344 -36    145    373*                                23I  15      16.6     0.258 -36    154    403*                                23J  16      12.0     0.258 -36    159    410*                                ______________________________________                                         *Yield stress present                                                    

EXAMPLES C24A, C24B and 25A to 25C

A group of SAE 10W-30 lubricating oils, Examples C24A, C24B and 25A to25C, were formulated by combining a base oil with a viscosity indeximprover, a pour point depressant, an ashless dispersant, and adetergent/inhibitor package ("DI package") in the amounts set forthbelow in Table 6 (amounts are given as weight percents).

                  TABLE 6                                                         ______________________________________                                                 C24A    C24B    25A      25B  25C                                    ______________________________________                                        Viscosity  7.0       7.0     7.0    7.0  7.0                                  Index                                                                         Improver                                                                      (Exxon ECA                                                                    13111)                                                                        Pour point --        0.2     --     --   --                                   Depressant                                                                    Example C3                                                                    Example C1 --        --      0.2    --   --                                   Example 1  --        --      --     0.2  --                                   Example 4  --        --      --     --   0.2                                  Ashless    2.0       2.0     2.0    2.0  2.0                                  Dispersant                                                                    (Amoco 9250)                                                                  DI Package 10.45     10.45   10.45  10.45                                                                              10.45                                (Amoco                                                                        PC800-4)                                                                      Base Stock 80.55     80.35   80.35  80.35                                                                              80.35                                (Pennzoil HF                                                                  150N)                                                                         ______________________________________                                    

The kinematic viscosity of each of Examples C24A, C24B and 25A to 25Cwas measured by the method of ASTM D445-88. The pour point of each ofthe Examples was measured by the methods of ASTM D 97-87 and Cycle "C".The viscosity of each of the Examples was measured by ASTM D4684-89using a mini rotary viscometer (MRV).

Results are set forth below in Table 7 as viscosity (centiStokes), ASTMpour point (°C.), MRV viscosity (Poise) and borderline pumpingtemperature (BPT, °C.).

                  TABLE 7                                                         ______________________________________                                        EX. NO. C24A     C24B     25A    25B    25C                                   ______________________________________                                        100C Vis.,                                                                             11.16   11.23    11.11  11.22  11.19                                 cSt                                                                           CCS Vis.,                                                                             3100     2860     3060   2910   2840                                  -20° C.                                                                ASTM    -18      -33      -36    -30    -30                                   Pour                                                                          Point, C                                                                      Cycle C -33      -33      -33    -33    -30                                   Pour                                                                          Point, C                                                                      TP-1     35.2    32.6     16.7   34.0   34.7                                  MRV, P,                                                                       -20° C.                                                                TP-1     81.9    69.9     77.1   77.6   74.6                                  MRV, P,                                                                       -25° C.                                                                TP-1    205      189      197    210    201                                   MRV, P,                                                                       -30° C.                                                                TP-1    720*     589      620    680    618                                   MRV, P,                                                                       -35° C.                                                                TP-1    -31.6    -32.2    -32.0  -31.7  -32.0                                 MRV                                                                           BPT, C                                                                        MRV, P,  39.7    31.4     36.2   32.8   33.6                                  -20° C.                                                                MRV, P, 105      70.5     73.6   77.8   74.6                                  -25° C.                                                                MRV, P, 544*     182      186    207    190                                   -30° C.                                                                MRV, P, --       521      560    608    533                                   -35° C.                                                                MRV BPT,                                                                              -28.4    -32.6    -32.3  -31.9  -32.4                                 ______________________________________                                         *Yield stress present                                                    

EXAMPLE 26

A group of lubricating oil samples, Examples 26A to 26O, were formulatedby adding a pour point lowering copolymer or a 50/50 wt % mixture of twodifferent pour point lowering copolymers to an SAE 15W-40 lubricatingoil (Imperial PL 23720-1) at a level of 0.08 weight % copolymer solids.The pour point of each Example was measured by the "Cycle C" test methodand the apparent viscosity of each of the Examples was measured by themethod of ASTM D 4684-89 at -20° C. and -25° C. using a mini-rotaryviscometer.

The pour point lowering copolymers are identified (EX. No.) and theCycle C pour point (°C.) and the apparent viscosity (Poise) at -20° C.and -25° C. are given below in Table 10 for each of Examples 26A to 26O.

                  TABLE 10                                                        ______________________________________                                                       CYCLE C     Viscosity                                          ADDITIVES      POUR POINT  (Poise)                                            EX. No.                                                                              (EX. NO.)   (°C.)                                                                              -20° C.                                                                       -25° C.                          ______________________________________                                        26A    C1          -12         Solid  Solid                                   26B    C2          -33         162    436*                                    26C    C1/C2       -36         157    415*                                    26D    7/11        -36           99.8 265                                     26E    18/12       F-39        106    253                                     26F    7/C2        -36         109    288*                                    26G    8/C2        -33         103    287                                     26H    C1/11       F-39        106    271*                                    26I    C1/12       F-39        109    284                                     26J    9/13        -36           98.1 230                                     26K    10/14       -30         107    265                                     26L    9/C2        -33         101    254                                     26M    10/C2       -36         111    267*                                    26N    C1/13       -33         162    408*                                    26O    C1/14       -33         112    257*                                    ______________________________________                                         *Yield stress present                                                    

The pour point lowering copolymer of the present invention includes alarge relative amount of repeating units derived from lower alkyl(meth)acrylate monomers. i.e., front greater than 30 mole percent toabout 65 mole percent monomeric units derived front a (C₁ -C₄)alkyl(meth)acrylate monomer, most preferably methyl methacrylate. Thecopolymer provides high performance as a pour point lowering additive ina wide range of base oils at a reduced cost relative to pour pointlowering copolymers that include a smaller relative amount of lower,i.e., C₁ -C₄, alkyl (meth)acrylate comonomeric units and a largerrelative amount of higher, i.e., C₈ -C₂₄, alkyl (meth)acrylatecomonomeric units.

We claim:
 1. A lubricating oil composition, comprising a lubricating oilbase stock and from about 0.05 weight percent to about 1.0 weightpercent of a random copolymer, said copolymer comprising:from about 15mole percent to about 67 mole percent first repeating units, each ofsaid first repeating units having the structural formula: ##STR7##wherein each occurrence of R₁ is independently H or methyl and eachoccurrence of R₂ is independently selected from the group consisting of(C₈ -C₁₅)alkyl; from about 3 mole percent to about 40 mole percentsecond repeating units, each of said second repeating units having thestructural formula: ##STR8## wherein each occurrence of R₃ isindependently H or methyl and each occurrence of R₄ is independentlyselected from the group consisting of (C₁₆ -C₂₄) alkyl; and from greaterthan 30 mole percent to about 65 mole percent third repeating units,each of said third repeating units having the structural formula:##STR9## wherein each occurrence of R₅ is independently H or methyl andeach occurrence of R₆ is independently selected from the groupconsisting of (C₁ -C₄) alkyl; and said copolymer having a number averagemolecular weight of about 20,000 to about 80,000 and a weight averagemolecular weight of about 50,000 to about 200,000.
 2. The composition ofclaim 1, wherein the copolymer comprises from about 25 mole percent toabout 60 mole percent first repeating units.
 3. The composition of claim1, wherein the copolymer comprises from about 25 mole percent to about40 mole percent first repeating units.
 4. The composition of claim 1,wherein the copolymer comprises from about 10 mole percent to about 35mole percent second repeating units.
 5. The composition of claim 1,wherein the copolymer comprises from about 15 mole percent to about 30mole percent second repeating units.
 6. The composition of claim 1,wherein the copolymer comprises from about 32 mole percent to about 50mole percent third repeating units.
 7. The composition of claim 1,wherein the copolymer comprises from about 35 mole percent to about 45mole percent third repeating units.
 8. The composition of claim 1wherein R₁, R₃ and R₅ are each methyl.
 9. The composition of claim 1wherein R₄ is selected from the group consisting of stearyl, cetyl,eicosyl and mixtures thereof.
 10. The composition of claim 1, wherein R₂is selected from the group consisting of isodecyl, lauryl, tridecyl,myristyl, pentadecyl and mixtures thereof.
 11. The composition of claim1, wherein R₆ is selected from the group consisting of methyl, n-butyl,isobutyl and mixtures thereof.
 12. The composition of claim 11, whereinR₆ is methyl.
 13. The composition of claim 1, wherein the copolymer hasa number average molecular weight from about 25,000 to about 70,000. 14.The composition of claim 1, wherein the copolymer has a number averagemolecular weight from about 28,000 to about 60,000.
 15. The compositionof claim 1, wherein the copolymer has a weight average molecular weightfrom about 50,000 to about 175,000.
 16. The composition of claim 1,wherein the copolymer has a weight average molecular weight from about50,000 and about 100,000.
 17. The composition of claim 1, wherein eachof the first repeating units is derived from a (C₈ -C₁₅)alkylmethacrylate monomer.
 18. The composition of claim 17, wherein the (C₈-C₁₅) methacrylate monomer is selected from the group consisting ofisodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate,myristyl methacrylate, pentadecyl methacrylate and mixtures thereof. 19.The composition of claim 1, wherein each of the second repeating unitsis derived from a (C₁₆ -C₂₄)alkyl methacrylate monomer.
 20. Thecomposition of claim 19, wherein the (C₁₆ -C₂₄)alkyl methacrylatemonomer is selected from the group consisting of stearyl methacrylate,cetyl methacrylate, eicosyl methacrylate and mixtures thereof.
 21. Thecomposition of claim 1, wherein each of the third repeating units isderived from a (C₁ -C₄)alkyl methacrylate monomer.
 22. The compositionof claim 21, wherein the (C₁ -C₄)alkyl methacrylate monomer is selectedfrom the group consisting of methyl methacrylate, n-butyl methacrylate,isobutyl methacrylate and mixtures thereof.
 23. The composition of claim22, wherein the (C₁ -C₄)alkyl methacrylate monomer is methylmethacrylate.
 24. The composition of claim 1, comprising about 43.9 molepercent first repeating units derived from lauryl methacrylate, about14.7 mole percent second repeating units derived from cetyl-eicosylmethacrylate and about 41.4 mole percent third repeating units derivedfrom methyl methacrylate.
 25. The composition of claim 1, comprisingabout 35.2 mole percent first repeating units derived from laurylmethacrylate, about 22.5 mole percent second repeating units derivedfrom cetyl-eicosyl methacrylate and about 42.3 mole percent thirdrepeating units derived from methyl methacrylate.